DSA Infix to Postfix

#include <iostream>
#include <ctype.h>
using namespace std;
char stack[100];
int top = -1;
void push(char c)
{
stack[++top] = c;
}
char pop()
{
return stack[top--];
}
bool empty()
{
return (top == -1);
}
bool isOperator(char x)
{
if(x == '+' || x == '-' || x == '*' || x == '/' || x == '^') return true;
else return false;
}
bool isOperand(char x)
{
if(isalpha(x) || isdigit(x)) return true;
else return false;
}
int precedence(char x)
{
switch(x)
{
case '+':
case '-':
return 2;
case '*':
case '/':
return 3;
case '^':
return 4;
}
}
string Infix_to_Postfix(string str)
{
string postfix = "";
int len = str.length();
for(int i = 0; i < len; i++)
{
if(isOperand(str[i])) postfix+=str[i];
else if(str[i]=='(') push(str[i]);
else if(str[i]==')')
{
while(!empty() && stack[top]!='(')
{
postfix += stack[top];
pop();
}
pop();
}
else if(isOperator(str[i]))
{
if(empty() || stack[top] == '(' || precedence(stack[top]) < precedence(str[i])) push(str[i]);
else
{
postfix += stack[top];
pop();
push(str[i]);
}
}
}
while(!empty())
{
postfix += stack[top];
pop();
}
return postfix;
}
int main() {
string s;
cout<<"Enter Infix Expression (without spaces) : "<<endl;
cin>>s;
cout<<"Your Infix Expression is: "<<s<<endl;
cout<<"Your Postfix Expression is: "<<Infix_to_Postfix(s)<<endl;
return 0;
}